This invention relates to a chain, especially to a chain used on a bicycle.
Conventionally, a chain is composed of a plurality of links, each link comprising a pair of outer chain plates, inner chain plates, rollers, chain pin sleeves, and chain pins. The chain plates are typically shaped as a dumbbell, with a circular portion of the inner chain plate having a larger diameter than that of the outer chain plate, and the chain pin having a longer length than a width of a combination of the outer and inner chain plates and rollers to effectively combine all elements mentioned above. Thus, the chain pin protrudes from the outer chain plate.
Referring to FIG. 7, when a rider shifts from a higher gear ratio to a lower gear ratio, i.e., from a sprocket with a smaller diameter to a sprocket with a larger diameter, the chain is tilted and guided by a derailleur to the target sprocket. Since the outer chain plate 50 has a certain thickness and the chain pin protrudes from the outer chain plate, a tooth 601 of the smaller diameter sprocket 60 may urge a lateral end 502 of the outer chain plate 50 or the protruding chain pin to tilt the chain, so as to cause a larger "twisting angle" of the chain between the two sprockets. Such a condition will cause the chain to easily be broken.
It is the purpose of this present invention, therefore, to mitigate and/or obviate the above-mentioned drawback in the manner set forth in the detailed description of the preferred embodiment.